This invention related to an improved molded rubber lug sole for footwear. Presently, conventional rubber lug soles have a bottom surface from which integral lugs extend downwardly. The lugs all have the same composition and hardness and are disposed about the periphery of both the sole and the heel portions. The lugs are shaped and spaced-apart from each other such that the soles will adhere to or "grip" the underlying ground surface in the same manner as rubber tires "grip" the road.
Lug soles are made in two basic styles. Conventional soles have a sole portion and a connected thin heel-attaching portion. Separate conventional heels are used with such conventional soles. A relatively recent innovation is the unit sole which combines the sole and the heel in one integral "unit sole". The present invention can be utilized by both styles.
At present, lug soles are tuypically molded from a single slug of synthetic rubber which is sufficiently hard so that the lugs will adequately support the weight of the wearer even in extreme conditions. Unfortunately, when the lugs have this hardness, typically about 85 Shore A hardness, the lugs tend to slip on hard underlying surfaces, such as rock. Obviously, such a slipping tendency creates a danger to a wearer who is hiking on a rocky trail or who is climbing up a rocky incline.
On the other hand, some present lug soles are made of softer synthetic rubber. However, softer lugs do not provide adequate support to a wearer in crucial situations where high stresses occur. Thus, a sole with soft lugs would be inadequate for the serious hiker or climber.
Accordingly, it is the object of this invention to provide a lug sole which has sufficient hardness to adequately support the wearer's weight even in extreme situations, and which has sufficient softness to provide good adhesion even on rocky surfaces.